This invention relates to a rotary vane vacuum pump which has a housing, a pump rotor and a motor drivingly connected with the pump rotor. The pump rotor and the drive motor have respective stub shafts which are arranged end-to-end in the housing and are connected to one another by a coupling.
The connection of the drive motor to the pump rotor as well as the oil-sealing of the drive are effected, as a rule, by means of a great number of components. The coupling usually comprises two coupling halves as well as an elastomer element including adjusting springs and screw connections. Further, separate shield members for the motor bearing and the rotary bearing as well as a coupling housing are provided. It is further necessary to provide the stub shafts with shaft sealing rings. For this purpose conventionally shaft seal bearing boxes are used. The individual structural components have to be manufactured separately which is not only technologically complex and thus expensive but may lead to tolerance accumulations which may adversely affect the precise circular run of the components.
In German Offenlegungsschrift (application published without examination) 23 54 039 a rotary vane vacuum pump of the above-outlined type is described. The separately supported motor stub shaft is provided with a bearing box which is slidably supported in a bore of the coupling housing. The bearing box is provided with shaft seal rings between which a lubricant chamber is provided. At its end the bearing box is connected by means of a pin coupling with the rotor stub shaft which has an enlarged diameter. In such a known pump out-of-round runs have been experienced which require a soft support of the pins of the pin coupling in at least one of the parts that are to be connected with one another. This measure further adds to the manufacturing expense. Further, difficulties have been experienced in supplying lubricant to the stub shaft of the pump rotor. It has been found that the reason for this difficulty is the immediate vicinity of the pumping chamber of the rotor to the surfaces of the rotor bearing which are to be supplied with oil. Since it is desirable to provide a full lubrication for the slide bearings, lubricating oil continuously gains access to the pumping chamber and thus adversely affects the efficiency of the pump.